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Purchased a Gigabyte motherboard (GA-78LMT-USB3) with a new computer about a week ago. The keyboard is a Unicomp 101-key PS/2 keyboard, which is what I am using to type this question (i.e., the keyboard works).


Upon booting the new computer all keyboard LEDs flash. The computer is unresponsive to any keystrokes (i.e., I cannot enter the BIOS, issue a three-fingered salute, or toggle the lock keys). Effectively, the keyboard is dead.


Tried using a USB-to-PS/2 adapter, but the problem persists. Interestingly, the USB port seems to give the keyboard more power, as the LEDs flash brightly when plugged into the USB port (full power) but dimly when in the PS/2 port (low power).

I wanted to try a KVM switch, but the maximum resolution for KVMs (immediately available) is 2048x, which is shy of the 2560x that I use.

A different keyboard for new computer is responsive.


My questions:

  • Is the BIOS buggy?
  • Has anyone else experienced such an issue with Unicomp (or 101-key, PS/2) keyboards?
  • How would you resolve the problem?
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Are different keyboards a problem when used with the PS/2 port and with a USB port? Does a genuine USB keyboard work? Or is it only PS/2-style keyboards that are a problem? – Nicole Hamilton Mar 10 '13 at 6:21
I'd actually try the keyboard on a older system. I believe this is a well known issue as per my answer, though I need to look into how modern systems do PS/2 conversion to be sure. – Journeyman Geek Mar 10 '13 at 6:23
up vote 1 down vote accepted

Its probably not the motherboard, but rather the old gear and new gear not working together. The motherboard is probably fine, as is they keyboard, least as per the manufacturer's point of view.

Unicomp PS/2 keyboards are notoriously finicky about what they're plugged into - they draw somewhat more power than modern keyboards, and I'm guessing that the PS/2 port on your system just isn't giving enough. Considering a PS/2 port is legacy, chances are there's an interface chip that's just not good enough.

PS/2-> USB adaptors are also not made the same. A passive adaptor - which is basically a block of plastic with passthrough plugs would do you no good. You need an active adaptor - and as per my answer here the 'blue cube' type adaptor is the best bet.

enter image description here

Its supposed to be generic, but if memory serves me right, they have a cypress chip inside.

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Almost flawless. This solves the boot problem, but introduces a number of other problems. If I type certain keystrokes too quickly (over 110 wpm), then keys are dropped. I may have to get a USB version of the keyboard. "In response to these [power draw] complaints, Unicomp added USB models to their lineup." – Dave Jarvis Apr 1 '13 at 20:31

My Unicomp M keyboard would not work with a KVM switch - flashing lights, boot errors, the works. I found, however, that if I plug the KVM USB connectors into a separate addin USB card, by themselves, it works. I did this using an old USB2 card but it also works with a USB3 card. Note: when plugged into the USB3 card, I added an external USB powered disk and the keyboard started its light show. So, it definitely appears to be a power issue.

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